1. Field of the Invention
The present invention relates to a mechanism for feeding, advancing, and positioning web material, and in particular a mechanism for use in feeding edge perforated documents used in printers, teletypewriters, and the like.
2. Description of Related Art
Paper is often fed to high speed printers by a pair of tractors that have toothed belts which engage holes provided along the borders of the paper sheet. The toothed belts are often trained around two wheels, a drive wheel and an idler wheel. It is important that the belts move synchronously and in tandem so that both edges of the paper are advanced at the same rate and at the same time. For this reason, the drive wheels of both of the belts are typically driven by a single drive shaft. Another shaft, usually parallel to the drive shaft, is used to support the tractors. Documents come in varying widths and the spacing of the perforations with respect to the edge of the document may vary. Accordingly, the tractors must be positionable (i.e., movable axially) along the drive and support shafts. When the position of both tractors in proper alignment with the document perforations is obtained, the tractors must be fixed in position. The clamps must also be releaseable so as to allow for repositioning of the tractors for documents of varying width.
It is an object of the present invention to provide an improved feed mechanism for feeding of documents which mechanism may be positioned and clamped in position and wherein the foregoing difficulties and disadvantages are avoided.
It is a further object of the present invention to provide an improved document tractor which substantially reduces the possibility of interference between the document and the drive shaft.
It is a still further object of the present invention to provide an improved document tractor which reduces the likelihood of injury to the operator during feeding, adjustment or maintenance operations.
It is a still further object of the present invention to provide an improved document tractor which allows the operator to view documents directly during operation.
It is a still further object of the present invention to provide an improved document tractor which allows an operator to easily align the respective belts of a tractor pair such that the pins of such belts are in the same relative position with respect to the document being advanced.
It is a still further object of the present invention to provide an improved document tractor which increases ease of document loading, ease of clearing jams, and ease of attaining a maximum driving force.
The foregoing and other objects, advantages, and features of the invention as well as presently preferred embodiments thereof will become more apparent from a reading of the following description in connection with the accompanying drawings.